How to Restore Old Fireplaces

Make cardboard templates the exact sizes of the replacement hearth slabs and surround tiles. Use the slab templates when obtaining materials from your supplier. Use the tile templates to help lay out the desired design and determine the number of tiles needed.

If reusing the original mantle, outline its placement on the wall. Gently pry it away from the wall with pry bars. Measure the location of wooden elements---such as framing pieces---to ensure they are at least 2 inches from the firebox, or the distance required by local fire codes.

Protect the nearby floor with cardboard. Wear protective equipment, and use a demolition hammer to remove the original hearth stones. Apply only enough force with the hammer to chip away the stone slabs---pressing too hard will damage the supporting concrete base and firebox floor. Clean the hearth space with a brush and vacuum.

Make a screed---or piece to smooth concrete---from the 2-by-4 lumber piece. On each end, draw notches equal to the depth of the hearth stone slabs plus 3/8 inch for the thinset. Cut out the notches with the circular saw. Wet the hearth space. Mix the concrete topping with water in a bucket. Pour it into the hearth space. Lay the screed notch-side down over the concrete. It should fit easily into the hearth space, overhang the space approximately 6 inches on each side, and move back and forth freely across the entire area. Drag the screed across the hearth to smooth the concrete topping. Add more topping if necessary. Continue to smooth it with the screed until it is flat. Use a flat trowel to ensure all the corners are smooth. Let the topping dry overnight.

Mix the thinset mortar with water in a second bucket and pour it into the hearth space until 3/8-inch thick. Use the notched trowel to make even ridges in the mortar across the entire space. Using suction cups to help lift and handle the hearth stones, lay the stones into place on the thinset. Make sure the stones do not rock. Use additional thinset if the stones move or are too low in the hearth. Tap on the stones with the rubber mallet if they are too high. If necessary, add thinset between the hearth and firebox. With the brick trowel, remove any excess thinset and smooth the finished hearth.

Spread thinset on the back of the tiles with the notched trowel. Place tiles on the sides of the fireplace, pressing firmly against the bricks. Use a straightedge to ensure the tiles are even. If not, gently rotate them into place. Check that the inside pieces overlap the firebox slightly and that the top pieces are flush with the top of the fireplace. Let the mortar set overnight.

Place the mantle on the hearth, aligned with its earlier outline to judge its fit. If necessary, cut filler strips to ensure it fits snugly into place. Remove the mantle and glue and nail strips to the back of the mantle, cutting off excess lengths with the jigsaw. Center the mantle on the fireplace surround. Holding it tightly against the surround and wall, nail it into place by driving the finishing nails at an angle through the mantle and into the wall.